The Quality of Care Study has three objectives: first, to develop, apply and define those methods that are effective and operational for measuring the quality of care in a group practice, prepayment program; second, to estimate the cost of the operations of the medical care program; and third, to initiate improvement in the quality of care by correcting problems which will be identified. The Study suggests that the quality of medical care is appropriately measured by several variables, rather than by any single measurement. The variables are grouped under four categories: process of care, outcome of care, input to care, and access to care. The methodology employed to meet the study objectives is essentially to measure quality of care in terms of the four variables sets tested at a number of facilities in the Kaiser Permanente Medical Care Program, Southern California Region, to analyze correlations between the variables, to determine the costs of the measurement systems utilized and to initiate programs related to improvement in quality. The focus of efforts is related to questions of identifying feasible and effective measurements for quality of care in ongoing, prepaid group practice medical care programs. The Study is to be in four phases: research and design, implementation of assessment methods, analysis of results, efforts related to quality assurance.